Method and apparatus for treating cellulosic fabrics quickly with liquid ammonia

ABSTRACT

This disclosure teaches a method and a related apparatus for pretreating cellulosic fabrics with liquid ammonia to improve their comfort characteristics as well as their resistances to shrinking and wrinkling and to enhance their affinities for dyes, flame retardants, resins and the like and generally to condition the fabrics better for subsequent finishing operations. A fabric is impregnated with liquid ammonia and is subjected quickly (from about 0.6 to about 9.0 seconds and preferably from about 1.8 to about 3.6 seconds) to removal of the ammonia by drying the fabric so as to achieve these desired results without effecting substantial shrinking of the fabric. The time interval between the impregnation with and the removal of the ammonia from the fabric is controlled preferably by regulating speed of advance of the fabric and by regulating length of path of the fabric from the impregnation with the liquid ammonia to commencement of the removal.

United States Patent [191 Troope et al.

[4 1 Oct. 28, 1975 METHOD AND APPARATUS FOR TREATING CELLULOSIC FABRICS QUICKLY WITH LIQUID AMMONIA [75] Inventors: Walter S. Troope, Latham; Jackson Lawrence, West Sand Lake, both of NY.

[73] Assignee: Cluett, Peabody & CO., Inc., New

York, N.Y.

[22] Filed: July 16, 1973 [21] Appl. No.: 379,652

Related US. Application Data [63] Continuation-in-part of Ser. No. 106,514, Jan. 14,

1971, abandoned.

[52] US. Cl. ..8/125; 8/l49.1; 8/1492; 8/158 [51] Int. Cl. D06M l/02 [58] Field of Search 8/116 R, 125, 149.1, 149.2, 8/158 [56] References Cited UNITED STATES PATENTS 3,767,359 10/1973 Calamari et al. 8/125 X 3,849,067 1 H1974 Calamari et al. 8/125 X Primary ExaminerStephen J. Lechert, Jr.

57 ABSTRACT This disclosure teaches a method and a related apparatus for pretreating cellulosic fabrics with liquid ammonia to improve their comfort characteristics as well as their resistances to shrinking and wrinkling and to enhance their affinities for dyes, flame retardants, resins and the like and generally to condition the fabrics better for subsequent finishing operations. A fabric is impregnated with liquid ammonia and is subjected quickly (from about 0.6 to about 9.0 seconds and preferably from about 1.8 to about 3.6 seconds) to removal of the ammonia by drying the fabric so as to achieve these desired results without effecting substantial shrinking of the fabric. The time interval between the impregnation with and the removal of the ammonia from the fabric is controlled preferably by regulating speed of advance of the fabric and by regulating length of path of the fabric from the impregnation with the liquid ammonia. to commencement of the removal.

9 Claims, 10 Drawing Figures U.S. Patent Oc t.28, 1975 Sheet 1 of4 3,915,632

US. Patent Oct. 28, 1975 Sheet 3 of4 3,915,632

F I G. 4 7 I I DURATION OF LIQUID- 6 NO TENSION AMMONIA TREATMENT AA & sHRINKAOE REI.A l ENSION TIONS; IOO% COTTON I FABRIC; wARR DIREC- 4 2 LBS TION AT vARIOus I/ TENSIONS. 3 3LBS.

//A// 2 5I Bs. I 4 o I s. SHRINKAGE INAa O i I I 2 3 4 5 6 7 s 9 IO TIME IN sECONDs DURATION OF LIQUID- AMMONIA TREATMENT 3 F I G. 5 & SHRINKAGE RELA- TIONS; I00 "/0 COTTON 2 l/4 LB, TENsION FABRIC; FILL DIREC- K TION AT vARIOus I 2 TENSIONS.

SHRINKAGE IN 7., O 5 LBS.

I 2 5 4 5 6 7 8 9 IO TIME IN sECONDs 30 I80 FIG. 6 DURATION OF LIOIIIO- AMMONIA TREAT- I60 I MENT & BARIUM ,/-RANOE ACCEPTED As ACTIVITY NUMBEQ I50 RELATIONS; IOO% COTTON FABRIC. I40

I30 BARIUM ACTIVITY NO. 2 O

TIME IN SECONDS U.S. Patent Oct. 28, 1975 Sheet4 of4 3,915,632

7 UNTREATED 8 TREATED FOR ONE SECOND TREATED FOR FIVESECONDS FIG. IO

TREATED FOR THIRTY SECONDS METHOD AND APPARATUS FOR TREATING CELLULOSIC FABRICS QUICKLY WITH LIQUID AMMONIA CROSS-REFERENCE This is a continuation-in-part application with respect to copending application Ser. No. 106,514 filed Jan. 14, 1971, now abandoned.

BACKGROUND OF THE INVENTION Many fabrics customarily have been subjected to aqueous caustic soda solutions to mercerize fibers of the fabrics whereby the fibers swell; making them more porous and more accessible so that affinity for dyes, flame retardants, resins and the like is enhanced. However, caustic soda solutions degrade many fibers, so there is a need for a milder treatment which can achieve desired results of mercerizing without fiber degradation. Caustic mercerization also involves substantial washing to remove the caustic and this washing has been a drawback. Further, for various reasons, denims and corduroys have not lent themselves to caustic mercerization.

Liquid ammonia has been used for preshrinking of certain fibers and it has been used (as discussed in U.S.

' Pat. Nos. 3,511,591 and 3,347,963) for rendering cellulosic fibers more amenable to molding operations. Attempts to treat cellulosic fabrics with ammonia have been mentioned in German DAS 1,063,572 and in U.S. Pat. No. 1,998,551, but without favorable results having been attained. In U.S. Pat. No. 3,406,006 cellulosic fabrics treated with liquid ammonia produced excessive shrinking of the fabrics. In U.S. Pat. No. 3,560,140 yarns and threads were treated with liquid ammonia and thereafter were stretched to improve their strengths.

In U.S. Pat. No. 3,664,158 fabrics were treated with liquid ammonia and were subjected to transverse tensions to reduce shrinking, however, this attempt to limit shrinking of fabrics during liquid ammonia treatment was less than successful. Unfortunately application and control of such transverse tensions has not been feasible, especially in treating knitted fabrics. Even for woven fabrics, tensions required to limit the fabrics to 2 percent shrinkage were not truly practical and the problem was complicated further by seams in the fabrics. Fabric widths have been difficult to maintain, both because of shrinking by the liquid ammonia and because tensioning in the warp direction aggravates loss of width. Under presently applied techniques, tensioning has proven to be unsatisfactory in limiting shrinking in liquid-ammonia treatment of cellulosic fabrics.

The net result of the foregoing has been that, although liquid ammonia likely would be useful for mercerizing cellulosic fabrics (especially denims and corduroys), liquid-ammonia mercerizing truly had not achieved commercial practicality until the present invention.

SUMMARY OF THE INVENTION Problems of liquid-ammonia mercerizing of cellulosic fabrics have been solved (as will be set forth more fully herein) in a particularly novel, useful, unobvious and facile manner. It has been discovered that on contacting cellulosic fabrics with liquid ammonia, fibers of the fabrics first swell radially and become porous without substantial shrinking, then soon thereafter thefibers commence to shrink. The present invention provides a method and related apparatus for mercerizing cellulosic fabrics with liquid ammonia by immersing the fabrics in the liquid ammonia and then quickly removing the liquid ammonia from the fabrics (within from about 0.6 to about 9.0 seconds and preferably within from about 1.8 to about 3.6 seconds), before the fibers of the fabrics have an opportunity to shrink in any substantial amounts.

Accordingly, one object of the present invention is to use liquid ammonia instead of an aqueous caustic soda solution for mercerizing cellulosic fabrics so that the fabrics derive improved extensibility (or stretch), improved resistances to shrinking and wrinkling (or creasing) as well as enhanced affinities for dyes, flame retardants, resins and the like, all without degradation of fibers.

Another object of this invention is to enable mercerizing of many fabrics, such as denims and corduroys, which could not be mercerized practically by use of aqueous caustic soda solutions.

Still another object of this invention is to accommodate mercerizing of knitted fabrics by liquid ammonia.

Still another object of this invention is to control shrinking (especially of knitted fabrics) during liquidammonia mercerizing.

Still another object of this invention is to provide an apparatus of the type suggested which incorporates means for an operator to regulate speed of advance of the fabric and means to regulate length of path of the fabric from impregnation with the liquid ammonia to commencement of removal of the ammonia.

Still another object of this invention is to minimize tension requirements, so that mechanical requirements of the apparatus are simplified. Minimizing of tensions also reduces power needs of the apparatus.

Still another object of this invention is the use of an apparatus of the type suggested with a small treating volume so that necessary startup and shutdown periods are kept to a minimum.

Still another object of this invention is to furnish an apparatus of the type suggested that is economical to build and operate and is well suited otherwise to its intended function.

The apparatus is for carrying out treatment of cellulosic fabrics on an industrial scale. In order that this treatment might be done, it is necessary that the apparatus be capable of processing large quantities of fabrics with consistent and uniform results in a safe manner. Furthermore, it is important that the apparatus be capable of processing a wide variety of fabrics, light and heavy, low cellulosic content and high, loosely woven or knitted and tightly woven or knitted, etc.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat idealized elevational sectional view of an apparatus to carry out liquid-ammonia mercerizing of cellulosic fabrics.

FIG. 2 is a somewhat idealized plan view of the apparatus of FIG. 1.

FIG. 3 is an enlarged elevational schematic representation of a tension control system which forms a part of the apparatus.

FIG. 4 shows shrinkage and treatment time relations in the warp direction at various tensions for a cotton fabric.

FIG. 5 shows shrinkage and treatment time relations in the fill direction at various tensions for a cotton fabric.

FIG. 6 depicts barium activity number as a function of treatmenttime with liquid ammonia for a cotton fab- I'lC.

FIG. 7 is a photomicrograph of fibers from a cotton fabric untreated.

FIG. 8 is a photomicrograph similar to that of FIG. 7 for a cotton fabric treated for one second.

FIG. 9 is a photomicrograph similar to that of FIG. 7 for a cotton fabric treated for five seconds.

FIG. 10 is a photomicrograph similar to that of FIG. 7 for a cotton fabric treated for thirty seconds.

DISCUSSION AND DETAILED DESCRIPTION OF PREFERRED EMBODIMENT When a cellulosic fiber is immersed in liquid ammonia, the cellulose swells, in a manner similar to that when a cellulosic fiber is immersed in anaqueous caustic soda solution, thereby producing mercerization. The typical bean shape of a cellulosic fiber changes to a more cylindrical shape and walls of the fiber become thicker. In this condition the fiber is more receptive to dyes, flame retardants, resins and the like and is suited better otherwise to further processing.

When cellulosic fibers are spun into yarns and these yarns are woven into fabrics and then the fabrics are immersed in liquid ammonia, a considerable amount of lengthwise shrinkage occurs. For most commercial fabrics the shrinking is asymmetrical with more shrinkage occurring in the warp direction compared with that in the fill direction. FIG. 4 is a plot of shrinkage in the warp direction as a function of duration of liquidammonia treatment with various tensions applied to the warp for a cotton fabric. The curves from the 10 pound load to the 1 pound load were determined empirically and refer to tensions of 10 pounds to 1 pound per inch of fabric width respectively. The curve labeled No load is an extrapolated estimate of shrinkage which would occur under no load. The reason the no load curve was not determined experimentally was that an untensioned fabric wrinkles severely when placed in liquid ammonia and therefore shrinkage is extremely difficult to determine. The implication of FIG. 4 is that shrinkage can be restrained by tensioning the fabric. A similar effect is seen from FIG. 5 for shrinkage as a function of duration of liquid ammonia treatment at various tensions in the fill direction for a cotton fabric. It is evident that shrinkage is much less sensitive to both tension and time in the fill direction than in the warp direction and this is advantageous because it is difficult to apply tensions in the fill direction. However it should be noted that the general character of the curves in FIGS. 4 and 5 are similar, indicating that a similar means of control of the shrinkage in the fillrdirection is possible.

Treatment of a cellulosic fabric in liquid ammonia can result in undesirable shrinkage, but it also produces mercerizing effects. The result of fiber swelling in mercerizing is an increase in accessibility of cellulose by making it more porous and therefore more reactive. The practical benefits from this increased accessibility are higher dye affinity, increased resin affinity and the like, which (along with other benefits likewise obtained) are associated normally with aqueous caustic soda solution mercerizing.

A test method to determine degree of mercerization is covered in AATCC 89-l958T. This test is based on the fact that mercerized cotton absorbs more barium hydroxide than does untreated cotton, and so barium hydroxide may be used to determine quantitatively the extent of mercerization. In using this test it is important that no other barium ion absorbing materials be present, for example finishes or other fibers. Carefully scoured and cleaned specimens from a sample (and an unmercerized control) are immersed in 30 milliliter baths of 0.25N barium hydroxide, an alkali, for 2 hours at F. .10 milliliters of each solution are then titrated with 0.lN hydrochloric acid. The mercerized cotton sample will absorb a greater amount of barium hydroxide than will the control sample; therefore, the amount of barium hydroxide remaining in solution will be lower, and the amount of hydrochloric acid required for neutralization will be lower. The amount of hydrochloric acid required for neutralization thus becomes a quantitative measure of the amount of barium absorbed. The ratio of barium hydroxide absorbed by the mercerized specimen to that absorbed by the unmercerized specimen, multiplied by 100, gives a barium activity number. Values of to indicate no mercerization. A number above indicates substantially complete mercerization. Intermediate numbers usually indicate either an incomplete reaction or a weak mercerizing bath.

Typically mercerized samples should have a barium activity number of from 150 to to be considered properly mercerized. In FIG. 6 there is plotted an envelope of data on barium activity numbers taken on materials treated with liquid ammonia for various durations. Assuming that the representative curve for the data presented falls in the center of the envelope, it is approximated by the dashed median curve between 0 and 30 seconds.

Because the tests were performed on specimens of woven cotton fabric which are extremely large compared to their yarn sizes, the large specimens in effect averages activity for all of their yarns and hence for the fibers in the specimens. The photomicrographs of FIGS. 7 through 10 were taken from random yarns selected from the respective specimens. These yarns have been mounted in a medium which has been selected carefully not to effect the condition of swelling of cellulosic fibers. Specimens then were sliced into thin wafers in planes normal to their fiber axes and were photographed at 500 magnifications using light transmitted through the specimens.

The photomicrograph from an untreated control specimen is shown in FIG. 7 and reveals the typical bean shape of cotton fibers. A few of the fibers appear to be swollen and lack the bean shape; however, the number of these fibers is small compared to the total number of fibers shown in the photomicrograph. The photomicrograph for a yarn specimen given a I second liquid-ammonia treatment, as depicted in FIG. 8, shows a number of fibers on the outer surface of the yarn to be swollen while fibers near the center retain their classic bean shape. An inspection of the yarn which was treated for 5 seconds, as shown in FIG. 9, and the yarn which was treated for 30 seconds, shown in FIG. 10, indicates a larger number of fibers on the outside surface to be swollen. The yarns of FIGS. 7, 8, 9 and 10 were taken from fabrics which correlate with point 0, l, S, and 30 of time on the curve shown in FIG. 6. There is a significant difference in the degree of swelling (mercerizing effect) observed for liquid ammonia treated cotton fibers when compared to the untreated control cotton fibers. This clue and thesteep slope of the barium activity versus duration of liquid ammonia treatment curve in FIG. 6 led to a deduction, which was thereafter proven empirically, that satisfactory mercerization can be effected without undesirable shrinkage effects, provided the time for ammonia treatment of cellulosic fabrics is kept to a sufficiently short duration.

A preferred arrangement of apparatus for carrying out the method of this invention is shown in FIGS. 1, 2 and 3. A web 11 of a cellulosic fabric is advanced continuously through an ammonia treatment chamber 12 in which an immersion trough 13, a bow roller 14, a pair of padder rollers 15, a tension controller 16, a delay roller system generally designated 17 and a dryer 18 are housed. The fabric web 11 is fed through an inlet seal 19, around a roller 21 and under a wetting roller 22 into a pool 23 of liquid ammonia in the immersion trough 13. The immersion trough 13 has near its upper level a float 24 connected via an arm 25 to a switch 26. The switch 26 relates to a solenoid 27 which operates a valve 28 in a line 29. The line 29 feeds the immersion trough 13 via a line 31 penetrating into a cabinet 32 which encloses the chamber 12. During normal operation, a manual valve 33 is opened and another manual valve 34 is closed. For shutdown the valve 33 in the line 29 is closed and the valve 34 in the line 31 is opened. When the ammonia in the immersion trough 13 is to be changed rapidly, the contents in the immersion trough 13 may be emptied via a valve 35 and a line 36 into a pan 37 which is provided with a heating coil 38 to vaporize the ammonia therefrom for discharge via line 39 and vent 41 to suitable incineration or recovery means (not shown). The immersion trough 13 may be raised or lowered (as indicated by dashed lines in FIG. 1) to control immersion of the fabric web 11 into the pool 23 of liquid ammonia.

To avoid outleakage of ammonia it is desirable to maintain ammonia treatment chamber 12 at a slightly negative pressure. Toward this objective, vent 41 communicates with suitable exhaust means (not shown). The cabinet 32 is jacketed with an insulating material 42 interposed between an inner lining 43 and an outer lining 44. The inlet seal 19 and an outlet seal 45 each include pairs each of which pairs includes a resilient member 46 and an opposed stationary member 47. In each of the seals 19, 45, the fabric web 11 is engaged between a resilient member 46 and a stationary member 47 of each pair and the space between each of the pairs is evacuated via lines 48 and 49 respectively.

After being wetted with the liquid ammonia in the immersion trough 13, the fabric web 11 is delivered to the bow roller 14 which spreads and smooths the fabric web 11 before it passes between the padder rollers 15. Excess liquid ammonia removed from the fabric web 11 (by the action of the padder rollers 15 as well as by the action of the bow roller 14) is caught in a pan 52 for gravity-flow return to the immersion trough 13. From the padder rollers 15 the fabric web 11 is delivered to a roller 53 and thence over a series of alternating stationary rollers 54, 55 and movable rollers 56, 57.

This series of rollers comprises the delay system 17. The movable rollers 56, 57 are movable vertically as will be discussed in detail to control length of path of the fabric web 11 between the time it is impregnated with liquid ammonia in the trough 13 and the time removal of the liquid ammonia commences by drying of the fabric web. From the delay system 17 the fabric web 11 is, delivered to the heated, blanketed dryer 18 via a roller 59 whereby it is conducted on a blanket 61 over a drum 62. The blanket 61 is endless and it is cycled by means of rollers 63 over a heated drum 64. The fabric web 11 leaves dryer 18 via exit rollers 65 and the outlet seal 45 out of the ammonia-treatment chamber 12. Spraying of the fabric web with water or steam and redrying can also be employed thereafter to remove any ammonia that remains in the fabric.

FIG. 3 shows interconnection between the movable rollers 56, 57 and the tension controller 16. The movable rollers 56, 57 are mounted rotatably between a pair of vertically movable'support members 66, only one of which is visible in FIG. 3. A shaft 67 is threaded into a sleeve 68 affixed to the rear of the support member 66 whereby rotation of the shaft 67 in one direction effects downward movement of the support member 66 so as to shorten the path of travel of the fabric web 11 and to decrease the web tension, whereas rotation of the shaft 67 in the opposite direction effects upward movement of the support member so as to lengthen the path of the fabric web 1 1 and to increase the web tension. A bevel gear 69 is secured to an end of the shaft 67 and meshes with a bevel gear 71. The gear 71 is connected to a motor output shaft 72 of a reversible motor M. The motor M is of well known construction and is of a type wherein rotational direction of the motor is determined by the direction of current flow through either the armature or the field windings.

Switching means are provided between the tension controller 16 and the motor M to energize and control the rotational direction of the motor M in dependence upon the degree of tension in the fabric web 11, so that the movable rollers 56, 57 will be raised or lowered automatically accordingly to vary the web tension and maintain the web tension within a prescribed range. The switching means comprises a double-pole doublethrow contact switch having a pair of stationary contacts 73, 74 connected to one motor terminal and a pair of stationary contacts 75, 76 connected to the other motor terminal. A pair of movable contacts 77, 78 are disposed movably between the contacts 73 and 75, and 74 and 76, respectively, to make electrical contact therewith.

The movable contact 77 is connected to a positive source of voltage and the movable contact 78 is connected to a negative source of voltage through a pair of rigid conductor bars. The conductor bars are mounted pivotally to enable the movable contacts 77, 78 to pivot into contact with the stationary contacts. A lever L interconnects pivotally the conductor bars and the lever L is connected at its midpoint to the journal housing of the tension controller 16. By such a construction, tension variations in the fabric web 11 result in compres sion or expansion of the flexible confinement 79 accompanied by a corresponding downward or upward movement of the journal housing. If the web tension exceeds a certain value, the flexible confinement 79 is compressed sufficiently to cause the lever L to move the movable contacts 77, 78 downwardly into respective contact with the stationary contacts 75, 74, thereby energizing the motor M and effecting current flow in the direction of arrow i, to cause the motor M to rotate in the direction to lower the support member 66. The lowering of the support member 66 lowers the rollers 56, 57 to reduce accordingly the web tension and this continues until the tension reduces enough to fall within a prescribed range at which time the flexible confinement 79 expands sufficiently to move the movable contacts 77, 78 out of engagement with the stationary contacts 75, 74 and the motor M then shuts off.

A similar mode of operation occurs if the web tension falls below a certain value, except in this case the flexible confinement 79 expands to move the movable contacts 77, 78 upwardly into respective contact with the stationary contacts 73, 76 thereby energizing the motor M and effecting current flow in the direction of arrow i to rotate the motor M in the other direction to cause raising of the rollers 56, 57 accordingly to increase the web tension.

Speed of the fabric web can be controlled conveniently by regulating the speed of the dryer 18 or preferably the padder rollers 15.

The ammonia vapor and air mixture in the chamber 12 during normal operation is preferably in a range where the ammonia vapor constitutes in excess of 90 percent by volume of the mixture. Such 90 percent by volume of ammonia vapor is well above the explosion or combustible mixture range of ammonia vapor and air. When the apparatus is being started up the treatment chamber is filled with air and a large portion of such air must be purged, or removed from the chamber and replaced with ammonia vapor. Conversely, when the apparatus is being shut down, the ammonia and ammonia vapor must be removed from the treatment chamber. Because mixtures of air and ammonia vapor in a range wherein the ammonia vapor constitutes from about 15 percent to about percent by volume of the mixture are explosive (if sufficient heat or ignition is applied to the mixture) care must be exercised to keep exposure to that range at a minimum.

It will be apparent to those skilled in processing of fabrics that wide deviations may be made from the disclosed preferred embodiment without departing from the main theme of invention set forth in the claims. For example, other types of ammonia applicators (such as sprays) could be employed, other types of dryers could be used and other systems for speed and retension controls could likewise be employed.

We claim:

1. The method of treating with liquid ammonia fabrics having a content of cellulosic fibers, which comprises a. advancing continuously a web of fabric into a treating chamber,

b. impregnating the fabric with liquid ammonia,

c. conveying the impregnated fabric through an ammonia laden atmosphere and permitting the fabric to be reacted upon by the liquid ammonia,

d. thereafter commencing and effecting the rapid removal of the liquid ammonia from the impregnated fabric, and

e. controlling the length of the path of travel of the fabric web between said impregnating step and the commencement of said rapid removal step as a function of fabric tension during said conveying step, whereby to control the action of said liquid ammonia upon said fabric.

2. The method of claim 1, further characterized by a. said path of travel of the fabric web being controllably increased in response to a decrease in fabric LII tension, whereby to increase the effective reaction time between said fabric and liquid ammonia.

3. The method of claim 1, further characterized by a. said fabric being impregnated by being immersed in a body of liquid ammonia,

b. removal of said liquid ammonia being commenced by bringing the impregnated fabric into contact 1 with a heated drum surface, and

c. said fabric being confined by a belt against said drum surface during removal of the liquid ammonia.

4. The method of claim 3, further characterized by a. the time period from the initial impregnation of the fabric until commencement of removal of the liquid ammonia being between 0.6 and 9.0 seconds.

5. The method of claim 4, further characterized by a. the time period from the initial impregnation of the fabric until commencement of removal of the liquid ammonia is from about 1.8 to about 3.6 seconds.

6. The method of treating with liquid ammonia fabrics having a content of cellulosic fibers, which comprises a. advancing continuously a web of fabric into a treating chamber,

b. impregnating the fabric with liquid ammonia,

c. conveying the impregnated fabric for a controllable period and through a controllable path while permitting the liquid ammonia to react upon the cellulosic fibers,

d. thereafter commencing and effecting the rapid re moval of said liquid ammonia from said fabric in order to terminate the reaction of said ammonia on said cellulosic fibers,

e. sensing the tension in the fabric during said conveying step, and

f. controllably increasing and decreasing the length of said path as necessary to maintain said tension within predetermined limits.

7. The method of claim 5, further characterized by a. sensing tension in said fabric in the warp direction,

and

b. increasing or decreasing the length of said path in an inverse relation to the tendency of the warp direction tension in said fabric to increase or decrease.

8. Apparatus for the liquid ammonia treatments of fabric webs, which comprises a. means for continuously advancing a web of the fabric,

b. means for impregnating the advancing web with liquid ammonia,

c. means for conveying the impregnated fabric through a controllable path while said liquid ammonia is reacting with the fabric,

d. means for commencing and effecting the rapid removal of the liquid ammonia from the fabric,

e. means for sensing the warp-direction tension in the ammonia impregnated fabric while the fabric is being conveyed to said last mentioned means, and

f. means for controllably diverting the path of said impregnated fabric as a function of said tension for increasing or decreasing the period during which said liquid ammonia is acting upon said fabric.

9. Apparatus according to claim 8, further characterized by 9 10 a. said means for sensing comprising a sensing roller other of them to alter the path of the fabric, and

engaging one surface of the impregnated fabric 0. said means to move said one roller comprising a web across its width, positioning motor and means for activating said pob. said means for diverting comprising a plurality of sitioning motor in response to fabric tensions rollers engaging the fabric across its width and 5 sensed by said sensing roller. means to move at least one of them relative to an- 

1. THE METHOD OF TREATING WITH LIQUID AMMONIA FABRICS HAVING A CONTENT OF CELLULOSIC FIBERS WHICH COMPRISES A. ADVANCING CONTINUOUSLY A WEB OF FABRIC INTO A TREATING CHAMBER, B. IMPREGNATING THE FABRIC WITH LIQUID AMMONIA C. CONVEYING THE IMPREGNATED FABRIC THROUGH AN AMMONIA LADEN ATMOSPHERE AND PERMITTING THE FABRIC TO BE REACTED UPON BY THE LIQUID AMMONIA D. THEREAFTER COMMENCING AND EFFECTING THE RAPID REMOVAL OF THE LIQUID AMMONIA FROM THE IMPREGNATED FABRIC AND E. CONTROLLING THE LENGTH OF THE PATH OF TRAVEL OF THE FABRIC WEB BETWEEN SAID IMPREGNATING STEP AND THE COMMENCEMENT OF SAID RAPID REMOVAL STEP AS A FUNCTION OF FABRIC TENSION DURING SAID CONVEYING STEP WHEREBY TO CONTROL THE ACTION OF SAID LIQUID AMMONIA UPON SAID FABRIC.
 2. The method of claim 1, further characterized by a. said path of travel of the fabric web being controllably increased in response to a decrease in fabric tension, whereby to increase the effective reaction time between said fabric and liquid ammonia.
 3. The method of claim 1, further characterized by a. said fabric being impregnated by being immersed in a body of liquid ammonia, b. removal of said liquid ammonia being commenced by bringing the impregnated fabric into contact with a heated drum surface, and c. said fabric being confined by a belt against said drum surface during removal of the liquid ammonia.
 4. The method of claim 3, further characterized by a. the time period from the initial impregnation of the fabric until commencement of removal of the liquid ammonia being between 0.6 and 9.0 seconds.
 5. The method of claim 4, further characterized by a. the time period from the initial impregnation of the fabric until commencement of removal of the liquid ammonia is from about 1.8 to about 3.6 seconds.
 6. The method of treating with liquid ammonia fabrics having a content of cellulosic fibers, which comprises a. advancing continuously a web of fabric into a treating chamber, b. impregnating the fabric with liquid ammonia, c. conveying the impregnated fabric for a controllable period and through a controllable path while permitting the liquid ammonia to react upon the cellulosic fibers, d. thereafter commencing and effecting the rapid removal of said liquid ammonia from said fabric in order to terminate the reaction of said ammonia on said cellulosic fibers, e. sensing the tension in the fabric during said conveying step, and f. controllably increasing and decreasing the length of said path as necessary to maintain said tension within predetermined limits.
 7. The method of claim 5, further characterized by a. sensing tension in said fabric in the warp direction, and b. increasing or decreasing the length of said path in an inverse relation to the tendency of the warp direction tension in said fabric to increase or decrease.
 8. Apparatus for the liquid ammonia treatments of fabric webs, which comprises a. means for continuously advancing a web of the fabric, b. means for impregnating the advancing web with liquid ammonia, c. means for conveying the impregnated fabric through a controllable path while said liquid ammonia is reacting with the fabric, d. means for commencing and effecting the rapid removal of the liquid ammonia from the fabric, e. means for sensing the warp-direction tension in the ammonia impregnated fabric while the fabric is being conveyed to said last mentioned means, and f. means for controllably diverting the path of said impregnated fabric as a function of said tenSion for increasing or decreasing the period during which said liquid ammonia is acting upon said fabric.
 9. Apparatus according to claim 8, further characterized by a. said means for sensing comprising a sensing roller engaging one surface of the impregnated fabric web across its width, b. said means for diverting comprising a plurality of rollers engaging the fabric across its width and means to move at least one of them relative to another of them to alter the path of the fabric, and c. said means to move said one roller comprising a positioning motor and means for activating said positioning motor in response to fabric tensions sensed by said sensing roller. 